Frozen songwriting collaborators Robert Lopez and Kristen Anderson-Lopez reveal the story behind "Let It Go."

Robert Lopez and Kristen Anderson-Lopez
Joseph Marzullo/WENN

Inspired by the Hans Christian Andersen fairytale "The Snow Queen," the writers happily reveal that their latest hit project "Frozen" takes a contemporary page from the songwriting bible of collaborators Alan Menken and Howard Ashman, whose work together invigorated Disney's animated films with detailed, character-driven songs that feel as though they lept off the Broadway stage.

"I just wrote a thank you letter to Alan Menken telling him that he created the architecture and we're just living in it," Lopez confessed. "He and Howard really created this form and brought it to where it is now - all we did was try and write one of those." Added Anderson-Lopez, "The entire time we were working, we had the creed: 'What would Ashman do?'"

That formula sent "Frozen" skating away from the box office with nearly $1 billion in worldwide grosses since its release last November, while the breakaway single "Let It Go," performed by Tony winner Idina Menzel in the film and covered by pop star Demi Lovato, has turned into a YouTube phenomenon.

"We didn't know it was going to be this kind of hit until super duper late in the game," Lopez admitted. "We were just trying to..." "Not suck," Anderson-Lopez interjected laughing.

The couple are not strangers to juggernaut success. Lopez is the Tony, Grammy and Emmy Award-winning writer of The Book of Mormon, Avenue Q and the children's series "The Wonder Pets," and along with Anderson-Lopez, whose work includes In Transit, Finding Nemo - The Musical and the 2011 film "Winnie the Pooh," they could complete their mantle of honors at the Academy Awards on March 2. Their song "Let It Go" from "Frozen" is Oscar-nominated for Best Achievement in Music Written for Motion Pictures, Original Song. Should "Let It Go" win, Lopez will become one of the select group of writers to have won the Emmy, Grammy, Oscar and Tony Awards.

The writers recall the moment the hook to the driving ballad was born. "In a meeting I pitched, 'What about "Let It Go" because she's letting go of her whole past, but she's also letting go of all of this power she's been holding back?' And everyone said, 'That sounds like a hook!'"

They were guided by the casting of Tony Award-winning actress Idina Menzel, known for putting her indelible stamp on the Wicked power ballad "Defying Gravity," who would take on the role of Elsa, the princess whose uncontrollable powers blanket her entire kingdom in a permanent winter.

"That definitely influenced our choices as far as where we set songs lower in her range where she has that beautiful vulnerability and fragility," Lopez said. "Obviously, the chorus would be a huge belt that would just go into the stratosphere."

Listening to artists such as Aimee Mann, Tori Amos, Adele and Katy Perry for inspiration helped the writers to craft "a soulfulness and a sadness at the beginning, but then to also find the joy in all of her power by the end," Lopez explained.

Anderson-Lopez laughed recalling a walk in Brooklyn's Prospect Park that gave shape to the opening lyrics of the song. "We were in this kind of emo place of imagining what it would be like to be this perfect person who messed up once, and was chased away from everything she has known and all the people she has been sacrificing for. So Bobby just improvised, 'The snow glows white on the mountain tonight, not a footprint to be seen...'"

Lopez interjects, "Actually, I sang it all the way up to, 'A kingdom of isolation and it looks like I'm the queen,' because I remember thinking that was hilarious that I came up with that."

Anderson-Lopez was quick to reply, "I looked at Bobby and I was like, 'Are you sure you're straight?'"

And they still remember the first time Menzel performed "Let It Go" for them. "We were at Stephen Oremus' house and Idina had just gotten the song," Anderson-Lopez remembered. "She was practicing to do it live at a Disney roll-out event, and she started riffing on our melody. I just got chills up and down my body. I'm so excited that a live audience is going to experience that at the Oscars."

In addition to surviving the pressures of Hollywood's awards season and working on high-profile multiple projects, including a stage adaptation of "Frozen," which Anderson-Lopez characterizes as being in "very early talks," the writers are also the parents of two young daughters.

"The big difference when we write together is that there always has to be a baby-sitter or a school day," said Lopez. "We have two kids and we usually have just dropped them off at school when we get to start writing."

Full-time parenting while writing a major feature film may pose its challenges, but it also comes with its advantages. The writers have an at-home test audience comprised of their target demographic who are happily at their disposal.

"We played every demo for them first, really. We'd get home and whether they wanted to hear it or not, we'd play it before dinner," Lopez said. "If they were quiet during it and asked to hear it again, we'd usually send it right along to Disney. If not, it was back to the drawing board."

And before Menzel, Demi Lovato or even YouTube can lay claim to "Let It Go," the Lopezes point out that the song truly belongs to their daughters, Katie and Annie. "They're a little strange about other people singing 'Let It Go.' They're like, 'Yeah, yeah, that's so 2012.'" Anderson-Lopez laughed.

Elsa sings "Let It Go."

Photo by Disney

They can also be heard in the film. "Katie, our eight-year-old, sings the first verse of 'Do You Wanna Build a Snow Man?,'" Anderson-Lopez said. "She did a lot of demos for us all throughout the process. She's also on the deluxe album, and there are a bunch of outtakes on there and you hear her voice quite a bit. And our youngest daughter, Annie, plays the baby troll who says, 'By the way, I don't see no ring!' She likes to go up to people all over and say, 'Do you know 'Frozen'? I'm, 'By the way I don't see no ring!'"

Their role as parents also served as a touchstone for the message they wanted to impart with "Frozen," not just to their daughters, but to young women everywhere. Without spoiling the film, "Frozen" turns the fairytale storybook ending on its head, proving that it's not always the prince who comes to the rescue - and that true love doesn't always come riding into town wrapped in shining armor.

"Everything that we wrote in this movie was written from a place of, 'What can we write to help make this world a better place for our daughters?,'" Anderson-Lopez said. "Every lyric and every choice that we had the characters make [was written with that in mind]. Whenever anything was suggested that felt wrong, as a parents of two daughters, we'd say no." Lopez quipped, "There's nobody who hates handsome princes more than fathers of young girls."

In addition to their Academy Award-nominated music for the film, "Frozen" is also heading to the Oscars with a "Best Animated Feature" nomination, having already won the Golden Globe and BAFTA Awards in respective categories.

When asked what they were most looking forward to at the Oscars on March 2, Lopez replied, "I'm looking forward to meeting John Williams, my movie music hero." Ready with an honest zinger, Anderson-Lopez sighed, "I'm just looking forward to eating carbs again."